During photography using a digital camera or a video camera for consumers, recorded images are sometimes blurred due to movements of the zoom lens during image capture caused by the hands of the operator of the camera shaking or by other factors. In a known prior art technique for preventing such blurring of images, specified lenses of the imaging optical system are moved orthogonally to the optical axis in order to provide a function of preventing blurring of an image.
For example, a zoom lens including a function of preventing blurring of an image is disclosed in Japanese Laid-Open Patent Application No. H06-337374. The zoom lens of Japanese Laid-Open Patent Application No. H06-337374 is a two-group zoom lens including, in order from the object side, a first lens group having negative refractive power and a second lens group having positive refractive power. In this zoom lens, the second lens group is moved orthogonally to the optical axis in order to prevent blurring of images due to movements of the zoom lens during image capture.
Japanese Laid-Open Application No. H01-167724 discloses an imaging optical system including multiple lens groups wherein a specified lens group is moved orthogonally to the optical axis in order to prevent blurring of images due to movements of the zoom lens during image capture. In Japanese Laid-Open Application No. H01-167724, the image magnification of this specified lens group is limited to be no larger than a certain value in order to limit the movement off the optical axis in a direction orthogonal to the optical axis required for the specified lens group to prevent blurring of the image being captured.
Additionally, the applicant of the present application disclosed a three-group zoom lens having high resolution in Japanese Laid-Open Patent Application No. 2004-240222. However, this zoom lens does not include a function of preventing blurring of an image.
Recently, there has been increased demand for zoom lenses that are compact overall and include a function of preventing blurring of an image accurately. However, the two-group zoom lens disclosed in Japanese Laid-Open Patent Application No. H06-337374, discussed above, wherein light emerging from the second lens group is nearly collimated before it reaches the image pickup surface, such as a CCD (charge coupled device), tends to have a large overall length, making it difficult to reduce the size of the zoom lens. On the other hand, quick response is required to accomplish highly accurate correction when image blurring movements, such as movements caused by hands shaking, occur. In order to obtain this quick response, it is desirable that the movement off the optical axis of the lenses being used to prevent blurring of a captured image be as small as possible. The imaging optical system of Japanese Laid-Open Application No. H01-167724, discussed above, has successfully reduced the movement off the optical axis required of the lenses being used to prevent blurring of a captured image. However, it does not provide sufficiently accurate correction for movements that cause blurring of a captured image as is desired for future use. Therefore, a zoom lens that more efficiently prevents blurring of a captured image while achieving more compactness is desired.